Infrared-Based Visualization of Wall Shear Stress Distributions

Rudolph, Ilka; Reyer, Matthias; Nitsche, W.

doi:10.1007/978-3-642-01106-1_24

Cited by 4 publications

(2 citation statements)

References 12 publications

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“…Details concerning these techniques and a discussion of the results have been published in [23] and are outlined in [21]. The visualized temperature difference due to wall shear rate in an air flow around a cylinder [22] …”

Section: Mixture Formation Analysis With Fluorescence Motion Analysismentioning

confidence: 99%

Spatiotemporal Image Analysis for Fluid Flow Measurements

Garbe

Kondermann

Jehle

et al. 2009

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Abstract. In this chapter, a framework will be presented for measuring and modeling transport processes using novel visualization techniques and extended optical flow techniques for digital image sequence analysis. In this way, parameters besides the 2-D xy velocity components can be extracted concurrently from the acquired 2-D image sequences, such as wall shear rates and momentum transport close to boundaries, diffusion coefficients, and depth z in addition to the z velocity components. Depending on the application, particularly the temporal regularization can be enhanced, leading to stabilization of results and reduction of spatial regularization. This is frequently of high importance for flows close to boundaries. Results from applications will be presented from the fields of environmental and life sciences as well as from engineering.

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Section: Mixture Formation Analysis With Fluorescence Motion Analysismentioning

confidence: 99%

Spatiotemporal Image Analysis for Fluid Flow Measurements

Garbe

Kondermann

Jehle

et al. 2009

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

View full text Add to dashboard Cite

show abstract

“…Thermographic flow visualization based on chemical surface treatment for the purpose of defect identification lacks in practicability or spatial resolution (Zhong et al, 2003;Kuester and White, 2016). Other studies investigated roughness elements that significantly exceed typical dimensions encountered on rotor blades (Rudolph et al, 2009). On airfoils and helicopter rotor blades, turbulent wedges were visualized by IRT without in-depth analysis (Horstmann et al, 1990;Kucaba-Piętal et al, 2013;Richter and Schülein, 2014).…”

Section: Introductionmentioning

confidence: 99%

Remote surface damage detection on rotor blades of operating wind turbines by means of infrared thermography

et al. 2018

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Abstract. Wind turbines are constantly exposed to wind gusts, dirt particles and precipitation. Depending on the site, surface defects on rotor blades emerge from the first day of operation on. While erosion increases quickly with time, even small surface defects can affect the performance of the wind turbine. Consequently, there is demand for an easily applicable remote monitoring method for rotor blades that is capable of detecting surface defects at an early stage. In this work it is investigated if infrared thermography (IRT) can meet these requirements by visualizing differences in the thermal transport and the corresponding surface temperature of the wall-bounded flow.Firstly, a validation of the IRT method compared to stereoscopic particle image velocimetry measurements is performed comparing both types of experimental results for the boundary layer of a flat plate. Then, the main characteristics of the flow in the wake of generic surface defects on different types of lifting surfaces are studied both experimentally and numerically: temperature gradients behind protruding surface defects on a flat plate and a DU 91-W2-250 profile are studied by means of IRT. The same is done with the wall shear stress from Reynolds-averaged Navier–Stokes simulations of a wind turbine blade. It is consistently observed, both in the experiments and the simulations, that turbulent wedges are formed on the flow downstream of generic surface defects. These wedges provide valuable information about the kind of defects that generate them. At last, experimental and numerical performance measures are taken into account for evaluating the aerodynamic impact of surface defects on rotor blades. We conclude that the IRT method is a suitable remote monitoring technique for detecting surface defects on wind turbines at an early stage.

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